Outlook: Problem with images in Signature Block

Please be aware that using images or backgrounds in
your emails, especially in signatures, may cause
some people to not receive attachments.

This is a flaw in Microsoft Outlook, and cannot
currently be fixed. The workaround is to remove
all images from signatures, and preferably go to
Tools>Options>Mail Format> and to:
       a) uncheck the "Use Microsoft Word to Edit Email messages"
       b) Compose in either HTML or Plain Text.

For further information, please see:
Microsoft Knowledge Base

Even though this article specifies Outlook 2000, we
have seen several instances where this is true with
Outlook 2002 (XP), as well as Outlook 2003.